Current supply apparatus



y 1960 c. F. SIMONE 2,936,404

CURRENT SUPPLY APPARATUS Filed Aug; 14, 1957 FIG. I

FIG. 2

TURN OFF INVENTOR B C. E SIMONE r .47 TORNEV United tes Patent r 2,936,404 CURRENT SUPPLY APPARATUS Carl F. Simone, Florham Park, N..l., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Application August 14, 1957, Serial No. 678,218

7 Claims. (Cl. 315-130) This invention relates to currentsupply apparatus and" particularly to a current supply apparatus for selectively energizing indicating lamps of the cold cathode, gas-filled type.

An object of the invention is to provide apparatus for supplying a regulated, periodically varying voltage wave to a varying load.

There are known switching circuits, sometimes called flip-flop or bistable circuits, in which a transistor, forex amp1e ,is made conducting in response to a control pulse of 'on'e polarity and nonconducting in response'to a control pulse of opposite polarity. For testing and locating fau'l ts in circuits of this type, it is'desirable to employ neon' orother coldcathode, gaseous lamps to produce an indieati'oi't'of the conducting and nonconducting states of lamp' may'be 75' volts and its extinguishing voltage may be 60' volts while a typical bistable transistor circuit may have a'collectorpotential ofminus 2 volts-when conducting and a collector potential of minus 16 volts when nonconducting.

In accordance with a specific embodiment of the invention, herein shown and described for the purpose of illustration, there is provided for energizing a varying lo'ad comprising a plurality of neon lamps in parallel current paths, a regulated current supply circuit for impressing across the load a periodically varyingregulated voltage'wave. The current supply circuit comprises a resistor in'series with a direct-current supply sourceand the load and the space current path of a first space current device in a shunt path across the load. The resistance of the space current path of the first space current device is controlled from the output of art-amplifier comprising a'second space current device upon the control electrodeca'thodecircuit of which a control voltage isimpressed. The-control 'voltage comprises an average voltage component upon which an alternating voltage wave is superposed. The alternating voltage wave is derived from a source of rectified alternating voltage and comprises a sinusoidal pulse produced during alternate half-cycle periods of the alternating voltage and a substantially uniform voltage produced during. the remaining halt-- Thereis thus set up across the load a cycle periods. periodically varying unidirectional voltage wave having portions of substantially uniform amplitude during intermittent periods and sinusoidalpulses during intervals separating. the intermittent periods.

voltage irrespective of changes ofload;

The circuit comprising the series resistor and the space current devices functions to minimize changes of both the uniform voltage portions and the sinusoidal pulses oftheload.

, 2,936,404 Patented May 10, 1960 The invention will now be described in greater detail. with reference to the accompanying drawing of which;

Fig. 1 is a schematic view of a current supply circuit embodying the invention; and

Fig. 2 is a schematic view of a modification of a portion of the circuit shown in Fig. 1.

Referring now to the drawing, there is shown a circuit for supplying current from a direct-current supply source 10, a battery, for example, to a variable load 11 having a pair of load terminals 12 and 13. The grounded positive terminal of battery 10 is connected to load terminal 12 and the negative battery terminal is connected through a resistor 14 to the load terminal 13. The anode-cathode or space current path of a triode space current device 15 is connected in a shunt current path across the load 11, the cathode of tube 15 being directly connected to load terminal 13 and the anode being connected through an auxiliary direct voltage source or battery 16 to the load terminal 12;

A voltage divider comprising resistors 17 and 18 in; series is connected across the resistor 14 and a second voltage divider comprising resistors 19 and 20 in. series is" connected across the battery '10. There is provided a second space current device 21 having a control electrode connected to the common terminal of resistors 17and' 18and having a cathode connected to the common terminal of resistors 19 and 20. The anode of the tube 21 is" connected to groundthrough a resistor 22 and the auxiliary" battery 16' in series. The anode of tube 21 is also con nected' through a resistor 29 to the control electrode of tube 15. The control electrode of tube 21 is connected through a condenser 23 and a rectifier element 24 in its.- forward or low resistance direction to ground. Resistors? 25 and 26 in series are connected across the rectifier ele ment 24. There is provided an alternating current sup ply source 27 having one of its terminals connected to ground and its other terminal connected through a condenser 28 to the common terminal of resistors 25 and 26.: Resistors 14, 17, 18, 19 and 20 may have resistance: values of 6,000; 160,000; 270,000; 50,000 and 39,000 ohms, respectively. The capacitance of condenser 23 may be 20microfarads.

The load 11, as shown in Fig. 1, comprises a variable resistance 35 and a plurality of current paths each con nected across the 'load terminals 12 and 13. Each of- 10' in the circuit for supplyingcu'rrentto the currenti path. The variable batteries 32 and the variable resistance 35 are shown in Fig. 1 for the purpose of simplicity.

Instead of the variable resistance 35 and each ofthe:

batteries 32 there may be employed, as shown in Fig. 2,. a p-np type transistor 40 having its emitter connectedi to the grounded load terminal 12 and having itscollectoi" connected through resistor 31 and neon lamp 30 to the load terminal 13. The collector is connected through: a resistor 41 to a potential source which is 20 volts negative'with respect to ground. A positive 4.5 volt poten-- tial source is connected through an inductor 42 and a-. resistor 43 in parallel and, in series therewith, a resistor 44 to the base of transistor 40. Positivepulses A may be supplied to the base of the transistor through a rec-= tifying element 45. Negative pulses B may be supplied. to the base through rectifying element 46 and a corn denser 47 in series. When pulse A is applied, the tram-- sistor 40 is substantially nonconducting, the voltage drop across resistor 41 is relatively small and the potential at the common terminal of resistor 31and the collector" of transistor 40 "may be minus 16'volts with respect to; ground; for example; The potentialat tenninal' 13 may vary'fromhiinusfl "volts to minus 81 volts so'thaftliee amperes, for example.

voltage across the lamp 30 and resistor 31 in series will vary from 35 to 65 volts. The voltage required for firing a lamp 30 may be from 72 to 78 volts and the extinguishing voltage may be from 55 to 65 volts, for example. Therefore, when pulse A is applied the lamp 30 will be extinguished and will not refire. When pulse B is supplied to the transistor circuit, the transistor 40 is made conducting, the voltage drop across resistor 41 is relatively large and the potential at the collector of transistor 4i) becomes minus 2 volts with respect to ground, for example. The voltage across the lamp 30 and resistor 31 in series will, therefore, vary from 49 to 79 volts causing the lamp to be extinguished during alternate half-cycle periods and to be refired during each of the remaining half-cycle periods. The frequency of the alternating-current supply source 27 may be 60 cycles per second, for example. Because of the persistence of vision, the illumination produced by lamp 30 will appear to be continuous as long as the transistor 40 associated with the lamp is conducting. The potential at the collector of transistor 40 is shown at C, Fig. 2.

The number of transistors 40 and lamps 30 which are simultaneously conducting current may vary considerably. The load current may vary from zero to 15 milli- In considering the operation of. the circuit, let it be assumed initially that the voltage of the alternating-current supply source 27 is zero. Condenser 23 is initially charged bycurrent from battery through a circuit comprising resistors 25 and 26, condenser 23 and resistor 18, all in series, to make the control electrode of tube 21' negative with respect to ground. It is seen that the current flowing through resistor 14 is substantially equal to the current flowing through the load 11 plus the current flowing through the anodecathode path of tube 15. If the load current should increase, for example, to cause the current through resistor 14 to increase, the control grid of tube 21 becomes relatively more positive or less negative with respect to its cathode potential. As a result, the control electrode of tube becomes relatively more negative with respect to its cathode to cause the resistance of the space current path of tube 15 to increase. The space current flowing through the tube 15 thus decreases. The increase of current'through resistor 14 and of the voltage drop across resistor 14 are thus minimized. The load voltage is equal to the voltage of battery 10 minus the voltage drop across resistor 14. Therefore, when the voltage of the source 10 is substantially constant, the load voltage will also be maintained substantially constant irrespective of changes of load.

When the voltage of alternating-current source 27 is increased to a suitable operating value, during a halfcycle period of one polarity of the alternating voltage, current will flow through the series circuit comprising condenser 28, resistor 26 and rectifying element 24, all in series, to make the rectifier 24 conductive. During this half cycle period, the rectifying element 24 will maintain the common terminal of resistor 26 and condenser 23 substantially at ground potential. Subsequent to the initial charging of condenser 23, the potential of the control grid of tube 21 and, therefore, the potential of the control grid of tube 15, each with respect to its cathode, will-be substantially fixed during each half cycle period of this polarity. During the next half cycle period of opposite polarity, the rectifying element 24 is non-conducting and the potential of the common terminal of resistor 26 and condenser 23 with respect to ground will vary sinusoidally from zero to a negative peak amplitude and then back to zero as the voltage of the alternating current supply source increases from zero to a peak amplitude and then decreases to zero. The impedance of condenser 23 to thesine wave pulse is sufliciently low that the changes of potential at the common terminal of condenser 23 and resistor 26 will be impressed upon the control grid of tube 21. The half cycle sine wave pulse will make the control grid of tube 21' relatively more negative with respect to its cathode, thereby causing to be impressed upon the control electrode-cathode circuit of tube 15 a half cycle sine wave pulse making its control grid relatively more positive with respect to its cathode. This positive halfcycl e pulse impressed upon the control circuit of tube 15 causes an increase of voltage drop across resistor 14 and therefore a reduction of load voltage, the reduction of load voltage being pro portional to the instantaneous amplitudes of the sine wave pulse. 7

There is thus setup across the load terminals 12, 13 a periodically varying unidirectional voltage wave comprising a substantially steady average voltage component upon which an alternating voltage component is superposed. During half-cycle periods when rectifying element 24 isconducting, the voltage across load terminals 12, 13 has a substantially uniform amplitude larger than the average voltage. During half-cycle periods when rectifying element 24 is nonconducting, the load voltage is substantially a half-cycle sine wave pulse having a peak voltage less than the average voltage.

The regulating circuit operates not only to maintain the average voltage substantially constant but also to minimize amplitude changes of the superposed alternate flat top'and sinusoidal pulses. Suppose, for example, that the voltage of the alternating-current supply source 27 increases. As a result, the resistance of the anode- 'cathode'path of tube 15 decreases to cause a decrease of the load voltage across terminals 12, 13 and an increase of voltage across resistor 14. The increaselof:

voltage across resistor 14 makes the control electrode of tube 21 relatively more positive and the control electrode of tube 15 relatively more negative, thereby Opposing the decrease of resistance of the anode cathode path of tube 15 and minimizing the decrease of load voltage. By thus minimizing the amplitude changes of the average load voltage component and, of the flat top and sinusoidal pulses whichare superposed on the average component, both the magnitude and shape of the periodically varying load voltage wave are maintained sub stantially fixed.

What is claimed is:

1. Apparatus for supplying current from a directcurrent supply source to a varying load comprising a resistor in series with said supply source and said load, variable impedance means in a shunt path across said load, means for increasing the impedance of said impedance means in response to an increase in current flowing through said resistor and for decreasing the impedance of said impedance means in response to a decrease of current through said resistor and means for alternately.

increasing and decreasing the impedance of said impedance means,

2. Apparatus for supplying current from a directcurrent supply source to a varying load having a pair of terminals comprising a resistor in series with said supply source and said load, a current regulating device having a pair of principal electrodes and a control elec-- trode upon which may be impressed a potential with respect to the potential of one of said principal electrodes for controlling the current flowing through said device, direct-current conducting means for connecting said principal electrodes to said load terminals respectively, means for controlling the potential of said control electrode to cause the current through said device to increase in response to a decrease of current through said resistor and to decrease in response to an increase of current through said resistor and means for further controlling the potential of said control electrode to cause the current through said device to increase intermittently.

3. Apparatus for supplying current from a directcurrent supply source to a varying load comprising variable resistance means connected in a shunt direct-current path across said load, a resistor in series with said supply source and said load, said variable resistance means, said resistor and said load having a common terminal, means responsive to the current flow through said resistor for controlling the resistance of said variable resistance means to minimize changes of current flowing through said resistor, and means for intermittently further controlling the resistance of said variable resistance means to transiently change the current through said resistor.

4. Apparatus for supplying current from a directcurrent supply source to a load which may vary comprising a variable resistance means connected in a shunt direct-current path across said load, a resistor in series with said supply source and said load, said variable resistance means, said resistor and said load having a common terminal, means responsive to the current flowing through said resistor for controlling the resistance of said variable resistance means to minimize voltage changes across said load and means for further controlling the resistance of said variable resistance means for causing said load voltage to change during intermittent periods only.

5. A current supply circuit for supplying current from a direct-current supply source to a load which may vary, said load having a first and a second terminal, a first and a second space current device each having an anode, a cathode and a control electrode, means for connecting said anode of said first space current device to said first terminal, means for connecting said cathode of said first space current device to said second terminal, a resistor connected in series with said supply source and said load, a terminal of said resistor being connected to said second load terminal, a circuit connecting the control electrode and cathode of said second space current device, means for impressing upon said control electrodecathode circuit a portion at least of the voltage across said resistor, an increase of current through said resistor making the control electrode of said second space current device relatively more positive with respect to its cathode, means for connecting the anode of said second space current device to the control electrode of said first space current device and means for deriving from an alternating-current supply source and impressing upon the control electrode with respect to the cathode of said second space current device intermittent unidirectional pulses.

6. In combination, a plurality of similar indicating devices each requiring a firing voltage for initiating current conduction therethrough which is higher than the extinguishing voltage required for causing interruption of current conduction therethrough, a load comprising a plurality of current paths connected in parallel to a pair of load terminals, said current paths comprising said indicating devices respectively, a plurality of sources of varying direct voltage in said current paths respectively, each of said sources having a maximum and a minimum voltage such that the difference of said maximum and minimum voltages is less than the difference between said firing voltage and said extinguishing voltage, and means for impressing across said load terminals a second unidirectional voltage opposed. to the voltage in each of said current paths and larger than said maximum voltage, said second voltage comprising portions of relatively high amplitude during intermittent periods for initiating current conduction only in the current paths in which the direct voltage is relatively low and portions of relatively low amplitude during intervals separating said intermittent periods for causing interruption of the current flow in said current paths which are conducting.

7. In combination, a plurality of similar gaseous lamps requiring a firing voltage for initiating current conduction therethrough which is higher than the extinguishing voltage required for causing interruption of current conduction therethrough, a load comprising a plurality of current paths connected in parallel to a pair of load terminals, a plurality of transistors each having a collector, an emitter and a base, said current paths comprising the emitter-collector paths of said transistors respectively and said lamps respectively in series, means for setting up a varying voltage drop across said emittercollector paths respectively, the maximum variation of said voltage drop being less than the difference between said firing voltage and said extinguishing voltage, and means for impressing across said load terminals a voltage having portions of relatively high amplitude during intermittent periods for initiating current conduction only in the current paths in which said voltage drop is relatively low and portions of relatively low amplitude during intervals separating said intermittent periods for causing interruption of the current flow in said current paths which are conducting.

References Cited in the file of this patent UNITED STATES PATENTS 2,407,458 Spielman Sept. 10, 1946 2,697,201 Harder Dec. 14,1954

2,749,512 Blair June 5, 1956 2,790,132 Gilbert Apr. 23, 1957 2,791,719 Bliss May 7, 1957 FOREIGN PATENTS 472,326 Great Britain Sept. 22, 1937 

